Grinding mill



- Feb 25, 1936. FAHRENWALD 2,031,697

GRINDING MILL Filed April. 27, 1954 4 Sheets-Sheet l Feb 25, 1936 I A. w. F'AHRENWALD GRINDING MILL Filed April 27, 1934 4 Sheets-Sheet 2 K II I |I I I i H 3mm A W E l/#7677 WALD Feb. 25, 136. A. w. FAHRENWALD 2,931,697v

GRINDING MILL Filed April 27, 1934 4 Sheets-Sheet 3 Feb, 25, 19360 A. w. FAHRENWALD GRINDING MILL 4 Sheets-Sheet 4 Filed April 27, 1934 Patented Feb. 25, 1936 UNITED STATES PATENT OFFICE GRINDING MILL Arthur W. Fahrcnwald, Moscow, Idaho Application April 27, 1934, Serial No. 722,718

Claims. (Cl. 83--9) My present invention relates .to improvements rotary drum or shell 6 is provided with an axial in grinding mills in which the functions'of grindhub 1 by means of which the shaft and the drum ing or pulverizing by impact, and classifying or .are rigidly joined, and the hub is journaled in separating, are performed. Theseimprovements bearing 8, to provide for the turning of the drum 5 are here exemplified in a rotary ball mill with with the shaft 4., 5 which is embodied a classifier or separator, and By means of a ring gear 9, which is bolted to the by means of which classifier, the unclassified hub of the drum, power is applied for revolving material from the grinding chamber is returned the drum through the instrumentality of a small to the grinding chamberfor pulverization, to inpinion I0 mounted on the drive shaft l I, and the 10 sure a complete grinding of the material that latter is driven through the use of a pulley I2 10 passes through the mill. and appropriate power transmission means. The In carrying out my invention the grinding and drum or shell is thus mounted rigidly on one end classifying functionsareperformed on a 'fluid'ore of the power shaft 4, and the latter is supported pulp, as for instance a pulpof reduced ore, and and journaled in the bearings 5 and 8, to insure 5 the material is fed to'thegrindingchamber'with a smooth operation of the mill and equality in 5 a substantially constant'peripheral feed-and vdisthe balance of the rotary drum or shell of the charged to the classifying'tank throughan'axial mill. outlet from the grinding chamber. Arotary'icon- As shown, the drum or shell i f flattened, veyer .or rake operating with the'rotary'ball mill y d al s p av tapering heads, Which is employed for returning the course or unclassind to gu e the grinding ba Other grinding 20 'fied material to the feed tank forre-entry to'the media, and the material to be pulverized, toward grinding chamber, and these parts 'are combined e transve e Center Of t e e v g dru to and arranged in compact manner to insure e'ffiinsure th r qui d pu v z n i pa t a d indciency in operation, together with rapidity in the g of the Wet e p p and suitable liher plates passage of the material through the :mill, and at 3 are provided on the interior of the drum or 25 comparatively low cost .ofproduction andoperashell to compensate for wear. tion of the-min, The interior of the drum forms the grinding The invention consists in certain novel comchamber for the material, and the material iS fed binations and arrangements of parts as willzheret0 the te or of the drum throughtwo diametriinafter be more fully set forth and claimed; In a y a an p p a inlet p ts l4,v M in 30 the accompanying drawings Ihave illustrated one the circumferential Wall Of the drum, said ports complete example of the physical embodiment of being protected by means of p plates l5 my invention wherein the parts are combined Which guide the a al down he side of the and arranged according to one mode I have thus drum as it s fed to the interior of the drum.

far devised for the practical application of the Each p t s p v d d with an ak seven "5 35 principles of my i ve ti n, b t itwi11 :b d rof arcuate shape, mounted on the exterior of the stood that various changes and alterations .may drum, and the intake end of the scoop is fashioned be made in the exemplifying structure, within with an overhanging mouth [1, and a shovel-ledge the scope of my claims, without departing from Is at the outer side Of the mouth, for use as Will be 40 theprinciples of my invention. described. 40

Figure 1 is a view in elevation :at thefront or The Out from the interior of the drum, or feed side of the machine in which my invention from the grinding Chamber thereof, through is embodied. a central or axial screen or grate in the head Figure 2 is a vertical, longitudinal, sectional of the drum opposite to that of the shaft-head 5 view of the machine of Figure 1, as at line 2-2 of the drum. This outlet from the grinding chamof Figure 3. ber comprises a comparatively large ring I9 that Figure 3 is a view in elevation at the discharge is bolted to the head of the shell and the ring fits end of the machine. into the circular wall of an opening in the drum Figure 4 is a transverse, vertical seotional'view as best seen in Figure 2. The ring is fashioned .0 through the ball mill, as at line 44 of l igure 1. with an integral, outwardly flaring, discharge In the physical embodiment of my lnvent-ionI fl n e 20 v r which t tfl w n material haveshown the use of foundationsills L1, and. pours, and the material passes through spaces beams 2, 2, on which the main frame 3 is sup- 20a, that are formed by spokes 20b of the ring, ported, and the horizontally disposed power shaft as the drum revolves. These spaces are filled R5 4 is journaled at one end in bearingsi. The with tangentially arranged louvres 2!, arrangedin' series in the spaces, and the louvres are spaced apart to permit the wet slime or pulp to slide therethrough to the exterior of the drum.

The revolving drum is located in a feed tank 22, which as indicated encloses the lower portion of the drum, with the upper edge of the tank extending approximately to the longitudinal axis of the drum.

The reduced ore, or other crushed material, together with suflicient water to provide a wet ore pulp is fed in suitable manner to the feed hopper or mouth 23 of the tank 22, and the quantity of fluid pulp is governed or regulated to provide a water level, as indicated at W L in Figure 4. By an inspection of Figure 4 it will be apparent that the two scoops l6, l6, revolving with the drum, successively pass through the feed tank along the bottom thereof, and a charge of pulp is scooped from the tank and picked up as the drum revolves clockwise. As the scoop ascends with the revolving drum and the port I 4 passes the bottom median line of the tank, the charge in the scoop begins to slip through the port. By the time the scoop with its charge reaches the position of the scoop indicated at the upper left hand side of Figure 4, it will be apparent that the charge has slipped through the nozzle l4-!5, down the as cending side of the lower part of the drum, where it will mix with the tumbling grinding-media within the grinding chamber.

The quantity of material scooped in charges and passed to the grinding chamber from the feed tank is governed by the capacity of the scoops, as to size and number, and the capacity of the drum, to insure the maximum quantity with maximum efliciency of the grinding mill, and the two diametrically arranged intake ports or nozzles Hll 5 evenly distribute the material to the grinding chamber for pulverization by the grinding media or balls.

The speed of rotation of the rotary drum is also a factor in controlling the pulp or slime level in the grinding chamber, and by proper regulation the grinding action of the tumbling balls may be retarded or increased conforming to the speed of rotation of the drum and consequent feed of successive charges of slime to the grinding chamber.

In any event, the level of the wet pulp in the grinding chamber reaches a point where the pulverized material together with an undetermined quantity of coarse material will flow through the louvres of the outlet screen of the drum, and it will of course be understood that the screen prevents passage of the grinding media.

This overflow through the side screen of the drum falls into a classifier or separating chamber 24, which as indicated is a part of the feed tank, with the bottom of the classifying or separating chamber elevated a suitable distance above the bottom of the feed tank, and as indicated in Figure 2 the water level of the feed tank is also maintained in the classifying or separating compartment of the feed tank.

In the classifying chamber the finer particles, from which the coarser and heavier material is separated, together with the overflow of water, pass over a discharge outlet 25, and the level of this outlet or final discharge may be governed by the use of a vertically adjustable gate 26.

The ground material in suspension, at an elevation above the feed tank, is prevented from returning to the feed tank, but is floated 01f continuously at or near the surface of the water in the classifying chamber, and passes through the outlet for further treatment.

The unclassified material or coarse sand entering the classifying chamber sinks to the elevated bottom of the chamber, and from there is returned to the feed tank, mixed with the material to be ground and fed to the tank, and eventually passed through the mill until properly classified.

This unclassified material is returned to the feed tank by means of a spiral or screw conveyer 21, fashioned as a continuous blade, and of substantially the diameter of the drum, which latter as seen in Figure 2, has its bottom line disposed slightly above the bottom of the classifying chamber. The drum is spaced from the bottom of the classifying chamber a sufiicient distance to provide an elevated throat T between the classifying chamber and the feed tank, and the screw of laterally projecting arms 28 that are bolted at 29 to the exterior of the drum, and the lower portion of the conveyer is submerged in the water and pulp of the classifying chamber in order that the unclassified material may continuously be moved toward the throat T and be emptied into the bottom of the feed tank.

In addition to the natural fiow of water from the louvres toward the lowered edges of the outlet trough 25, the passage of the spiral conveyer or rake-blade 21 tends to create circulation of water in the classifying chamber that assists in carrying the classified material in suspension toward the outlet, and this circulation is accomplished without undue turbulence or agitation of the water.

As the submerged blade or rake moves the coarse material across the bottom of the classifying tank or pan toward the throat T, the spiral blade also tends to move the water at the bottom of the classifying chamber toward the throat. Thus, in Figure 2 the water at the bottom of the classifier is urged by the spiral rake to the left, and therefore a current at or near the surface of the water in the classifying chamber is induced to move to the right from the louvres toward the outlet trough, carrying with it the finely pulverized material. During this movement of the water toward the outlet, the coarse and heavier material sinks to the bottom of the classifying chamber in the path of the spiral rake, and the latter moves this material toward the throat T and into the feed tank. The outer edge of the spiral rake moves in close proximity to the bottom of the classifying chamber in order to rake the material therefrom and to continuously return this coarse sand to the feed tank.

The arcuate-shaped bottom of the classifying chamber is of course concentric with the semicircular shape of the feed tank, and the latter is provided with a drain 220, at its lowest point for use in emptying the classifying chamber and the feed tank when desired or necessary.

The appliance or mill, by means of which the fluid ore pulp is both pulverized and classified, is especially adapted for use in the reduction of ore, as for instance lead-zinc ore, and by the employment of the combined pul verizer and classifier in the treatment of the ore after it comes from the crushing machine, considerable time is saved in the steps necessary for the preparation of the finished or classified product; the use of a separate classifier is dispensed with;' and the classified material coming from the mill is of the required fineness for subsequent milling operations. I

The machine of my invention thus provides a most satisfactory unit that performs the required services with comparatively slight wear and tear and under comparatively low maintenance costs, and while I have referred to the pulverization and classification of reduced ore as the product of the machine, it will be understood that the machine may be employed in other industries for the performance of its functions.

It will be understood that various changes and alterations may be made in the exemplifying structure of my invention, within the scope of my appended claims without departing from the principles thereof.

Having thus fully described my invention, what I claim as new and desire to secure by Letters Patent is:

1. In a wet pulp grinding mill, the combination with a feed tank having a lateral classifying chamber, of a rotary drum partially submerged in said tank, said drum having a peripheral intake, and an axial outlet opening to said classifying chamber, and a conveyer rotatable with the drum for returning unclassified material from said chamber to the tank.

2. In a wet pulp grinding mill, the combination with a feed tank having a lateral classifying chamber, of a rotary drum having a peripheral intake and an axial outlet opening to the classifying chamber and partially submerged in said tank, and means mounted on and rotatable with the drum for conveying unclassified material from the chamber to said tank.

3. In a wet pulp grinding mill, the combination with a feed tank having a lateral classifying chamber, of a rotary drum partially submerged in said tank and having a peripheral intake and axial outlet to said chamber, and a spiral conveyer mounted on said drum for conveying unclassified material from the chamber to said tank.

4. In a wet pulp grinding mill, the combination with a feed tank having an elevated classifying chamber, of a rotary drum partially submerged in said tank and having a peripheral intake and an axial outlet, and a spiral conveyerbl'ade mounted at the outlet to said chamber side of the drum for returning unclassified material from said chamber to said tank.

5. In a wet pulp grinding mill, the combination with a feed tank having a lateral, elevated, classifying chamber, of a rotary drum partially submerged in said tank, said drum having an intake port and an exterior, arcuate, scoop for delivering charges through said port, said drum having an axial outlet to said chamber, and spaced louvres mounted in said outlet, and a spiral conveyer-blade mounted at the outlet side of the drum for returning unclassified material from said chamber to said tank.

ARTHUR W. FAHRENWALD. 

